1. Technical Field
The disclosure generally relates to optical lenses, and particularly relates to an optical lens to increase a viewing angle of a light source and a lighting device having the optical lens.
2. Description of Related Art
In recent years, due to excellent light quality and high luminous efficiency, light emitting diodes (LEDs) have increasingly been used as substitutes for incandescent bulbs, compact fluorescent lamps and fluorescent tubes as light sources of illumination devices.
Generally, light intensity of a light emitting diode gradually decreases from a middle portion to lateral sides thereof. Such a feature makes the LED unsuitable for functioning as a light source which needs a uniform illumination, for example, a light source for a direct-type backlight module for a liquid crystal display (LCD). It is required to have an optical lens which can help the light from a light emitting diode to have a wider viewing angle and a uniform intensity. Unfortunately, the conventional optical lens and a lighting device having the conventional optical lens can not obtain a satisfactory effectiveness.
What is needed, therefore, is an optical lens and a lighting device having the optical lens to overcome the above described disadvantages.